1. Field of the Invention
The invention relates to an apparatus for separating the flowable constituents from a mixture of flowable and non-flowable constituents particularly for the preparation of foodstuffs, the apparatus comprising a driven perforated drum having a perforated circumferential surface, a pressure belt enclosing part of the circumference thereof and pressable onto the same by means of at least one pressure roller, as well as a supply mechanism for supplying the product to be treated into an entry wedge formed between the perforated drum and the pressure belt.
2. Prior Art
The basic concept of such apparatus is that of a separator type, as disclosed, for example, in East German Pat. No. 96 155. The substance mixture introduced into such an apparatus and formed from flowable and non-flowable constituents is, after feeding and drawing into the wedge between the perforated drum and the pressure belt first pressed onto the perforated drum as a result of the radial pressure derived from the axial tension of the belt and in this way is supplied to the actual pressing point. This is formed by a pressure roller supporting the pressure belt and settable against the perforated drum, so that a pressure gap can be adjusted, in which, as a result of the elasticity of the pressure belt, the outflow of the flowable constituents through the perforations of the perforated drum into the interior thereof is effected through quasi-hydraulic pressure. In contrast thereto, the non-flowable constituents pass through the pressure gap accompanied by elastic embedding in the pressure belt and are subsequently stripped from the outer circumference of the perforated drum, if they have not been dropped already after release through the pressure gap.
Such apparatuses permit, in an uncomplicated manner, the separation of meat from tissues, bones and skin, so that they are mainly used in the production of sausages. However, as a function of the working product, particularly in the case of meat portions mixed, for example, with bone fragments, it has been found that when a small proportion of such fragments or other hard parts can, as a result of the particle size thereof pass in unhindered manner through the openings of the perforated drum. This also occurs in the case of longish particles, if they pass into the separator with a radial alignment with respect to the perforated drum.
Even in the case of an obvious use of such apparatuses for the unpacking and recovery of incorrectly packed flowable foods, such as cheese, butter, etc., accompanied by the simultaneous separation thereof from the packing material residues similar problems occur. These are manifested by an inadequate degree of purity of the recovered material. The reason for this is that the openings act as a punching die with respect to the pressure belt and the normally metallic, plastic or paper packaging or separating films or foils, as a function of the characteristics of the material thereof are punched out at least over single openings, so that said parts are floated out together with the outflowing material into the interior of the perforated drum. However, this phenomenon also occurs disadvantageously in the case of stronger films or foils, because, as a result of the pressure action, they are forced into the openings of the perforated drum, the packing material membranes formed over said openings at least partially bursting or splitting. The resulting perforations in the foils admittedly do not initially bring about a separation of foil particles, because the foils' tips forming at the perforation points with the flow of the outflowing food material are merely drawn into the openings without tearing off. However, when the packing material residues have left the pressing zone subsequently, then they remain in this state due to the positive anchoring in the openings, as well as to the generally effective adhesive forces on the circumferential surface of the perforated drum, so that constrained stripping is necessary. The equipment provided to this end comprises a stripping blade which scrapes over the circumferential surface of the perforated drum. Part of the foils' tips drawn into the openings are sheared-off, so that during the next revolution they are floated into the interior of the perforated drum together with the freshly squeezed out food material and lead to the soiling of the recovered material.
An apparatus disclosed in German Pat. No. 32 11 625 aims at eliminating this disadvantage. It is based on the idea that shearing is avoidable if, through the moving back of the material filling the openings in the perforated drum and which can be looked upon as a hydraulic medium, there is a floating back of the packing parts which have entered the openings prior to stripping by means of the stripping blade. The highly elastic inner roller provided for this purpose led to this effect, but this has led to a deterioration in output and yield, so that this apparatus has not become widely used for reasons of economy.
3. Objects of the Invention
It is therefore a major problem of the present invention to overcome these disadvantages by suggesting an apparatus permitting a better separation of flowable and nonflowable constituents from a mixture thereof. It is a further object of the invention to provide an apparatus which, in particular, permits the recovery of incorrectly packed viscous materials. It is yet another object of the invention to propose such apparatus which achieves a high output or yield and without impairing the purity of the resulting product.